1. Field of the Invention
The present invention relates to semiconductor laser apparatuses capable of emitting a plurality of light beams with different wavelengths, and manufacturing methods of such semiconductor laser apparatuses.
2. Description of the Background Art
Conventionally, semiconductor laser devices that emit infrared light with a wavelength of about 780 nm (infrared semiconductor laser devices) have been used as light sources in CD (Compact Disk)/CD-R (Compact Disk-Recordable) drives. Also, semiconductor laser devices that emit red light with a wavelength of about 650 nm (red semiconductor laser devices) have been used as light sources in DVD (Digital Versatile Disk) drives.
Meanwhile, the development of DVDs capable of recording and playback using blue-violet light with a wavelength of about 405 nm is recently proceeding. In order to play back and record such DVDs, the development of DVD drives using semiconductor laser devices that emit blue-light with a wavelength of about 405 nm (blue-violet semiconductor laser devices) is simultaneously proceeding. The DVD drives require compatibility with conventional CD/CD-Rs and DVDs.
Compatibility of a conventional CD or DVD with a new DVD is achieved by a method in which a plurality of optical pickups that emit infrared, red, and blue-violet light, respectively, are mounted in a DVD drive or by a method in which an infrared semiconductor laser device, a red semiconductor laser device, and a blue-violet semiconductor laser device are mounted in a single optical pickup. Such methods, however, cause increases in the parts count, thus making it difficult to produce smaller, simpler, and lower-cost DVD drives.
In order to prevent such increases in the parts count, an integrated semiconductor light emitting apparatus is suggested comprising a stack of a plurality of semiconductor light emitting devices with different wavelengths (refer to JP 2002-118331 A).
In the aforementioned integrated semiconductor light emitting apparatus, an InGaAlP-based 650-nm band semiconductor laser is formed on an InGaAlN-based 400-nm band semiconductor laser, for example.
In the apparatus comprising the stack of the InGaAlN-based 400-nm band semiconductor laser and the InGaAlP-based 650-nm band semiconductor laser, the InGaAlP-based 650-nm band semiconductor laser is more likely to be deformed by stress than the InGaAlN-based 400-nm band semiconductor laser.
Moreover, in the apparatus comprising the stack of an InGaAlN-based 400-nm band semiconductor laser and an AlGaAs-based 780-nm band semiconductor laser also, the AlGaAs-based 780-nm band semiconductor laser is more likely to be deformed by stress than the InGaAlN-based 400-nm band semiconductor laser. When the cavity facets of a semiconductor laser device are deformed by strain, the reliability thereof is reduced.